Interfacial and emulsifying properties of citrus pectin: Interaction of pH, ionic strength and degree of esterification

The interfacial and emulsifying properties of citrus pectin of different degree of esterification (DE = 55, 70 and 84%) were investigated. Ionic strength and pH were varied in order to modify the polyelectrolyte behavior of citrus pectins. The smallest hydrodynamic radius, lowest charge and fastest adsorption kinetics were found for high DE and high ionic strength at low pH. The extent of the dilational interfacial elasticity correlated with the amount and ratio of hydrogen bonds and hydrophobic interactions. The measured droplet sizes were mostly influenced by the adsorption kinetics and the salt responsiveness of citrus pectin. The faster the adsorption kinetics the smaller the resulting droplet sizes. Sodium chloride induced microgel particle formation of pectins. These microgel particles were less effective in droplet stabilization so that demulsification due to strong coalescence occurred. It was possible to counterbalance this effect by increasing the hydrocolloid emulsifier concentration.